Southwest German Interventional Study in Acute Myocardial Infarction - SIAM III

Description:

The goal of the SIAM III trial was to evaluate the efficacy of immediate stenting after thrombolysis versus a more conservative treatment regimen in patients with acute myocardial infarction (MI).

Study Design

Study Design:

Patients Enrolled: 163
Mean Follow Up: Six months (mean 287 days)
Mean Patient Age: Mean age 63 years
Female: 21
Mean Ejection Fraction: Mean baseline left ventricular ejection fraction 54.7%

Patient Populations:

Age >18 years; symptoms of MI present for <12 h; ST-segment elevation of ≥1 mm in ≥2 limb leads, ST-segment elevation of ≥2 mm in the precordial leads, or new bundle branch block; eligible for thrombolysis, meaning no history of stroke or central nervous system damage, recent major surgery, systolic blood pressure >200 mm Hg, or diastolic blood pressure >110 mm Hg at any time after arrival, no recent noncompressible vascular puncture, or concomitant use of an oral anticoagulant with an international normalized ratio >2; no secondary or iatrogenic infarction; and no chronic renal insufficiency requiring dialysis

Secondary angiographic inclusion criteria: indication for angioplasty independent of the study; and infarct-related lesion in a native coronary artery >2.5 mm with diameter stenosis of ≥70% or TIMI flow

Exclusions:

Secondary angiographic exclusion criteria: coronary anatomy unsuitable for stent placement; anticipated indication for surgical coronary revascularization within six months; previous MI in the area of the infarct-related vessel; or infarct-related lesion not clearly defined

Primary Endpoints:

Composite of death, reinfarction, ischemic events, and TLR at six months

Drug/Procedures Used:

All patients were enrolled at community hospitals without on-site catheterization laboratories. Patients received reteplase (two boluses of 10 MU 30 minutes apart) and were randomized to immediate transfer (within six hours of thrombolysis) to a larger facility for coronary angiography, including stenting of the infarct-related artery (IRA) (n=82) or elective coronary angiography two weeks after thrombolysis with stenting of the IRA (n=81).

Concomitant Medications:

Aspirin intravenously (250 mg) and heparin (bolus of 5000 IU + infusion of 1000 IU/h)

Principal Findings:

TIMI 3 flow rates at two-week angiography were 98% in the immediate stent arm versus 59% in the delayed stent arm (p<0.001). The primary composite endpoint of ischemic events, death, reinfarction, and target lesion revascularization (TLR) was significantly lower in the immediate stenting arm compared with the delayed stenting arm (25.6% vs. 50.6%, p=0.001). The reduction was driven primarily by the reduction in ischemic events (4.9% vs. 28.4%, p=0.01).

There was no difference in reinfarction (2.4% vs. 2.5%, p=0.685) or TLR (19.5% vs. 23.5%, p=0.336), but mortality was non-significantly lower in the immediate stenting arm (4.9% vs. 11.1%, p=0.119). Similar results were observed in an intention-to-treat basis (composite 29.8% vs. 53.4%, p=0.001). Patients with and without reperfusion after thrombolysis undergoing immediate stenting showed similar outcomes (composite 24.6% vs. 29.4%) in contrast with those patients with delayed stenting (composite 44.4% vs. 72.2%, p=0.001).

Ejection fraction was improved in the immediate stenting arm compared with delayed angiography both at two-weeks (56.7% vs. 52.5%, p=0.037) and six months (61.5% vs. 56.4%, p=0.018). There was no difference in major bleeding between the immediate stent group or the delayed angiography group (9.8% vs. 7.4%, p=0.400).

Interpretation:

Among patients with acute MI, treatment with an immediate facilitated percutaneous coronary intervention (PCI) strategy was associated with a reduction in the primary composite endpoint of death, reinfarction, ischemic events, and TLR at six-month follow-up compared with patients treated with thrombolysis and a two-week delay in PCI.

Findings are unlike trials in the 1980s, which did not show a benefit with thrombolysis and angioplasty, but did show increased bleeding. While primary PCI has been associated with improved outcomes in several trials, the availability of facilities with on-site catheterization labs is limited.

Additionally, transfer to such facilities routinely takes >1 hour in the United States, according to a recent National Registry of MI study. Given the importance of initiating early reperfusion therapy, data from the present trial suggest a combination of thrombolysis followed by early transfer for stenting may be optimal, both in patients with patent and occluded vessels at angiography. Further studies are warranted.

References:

Scheller B, Hennen B, Hammer B, et al., for the SIAM III Study Group. Beneficial effects of immediate stenting after thrombolysis in acute myocardial infarction. J Am Coll Cardiol 2003;42:634–41.

Clinical Topics: Anticoagulation Management, Arrhythmias and Clinical EP, Dyslipidemia, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, EP Basic Science, Lipid Metabolism, Interventions and Imaging, Angiography, Nuclear Imaging

Keywords: Myocardial Infarction, Stroke, Follow-Up Studies, Hospitals, Community, Blood Pressure, Fibrinolytic Agents, Constriction, Pathologic, Angioplasty, Stents, Percutaneous Coronary Intervention, International Normalized Ratio, Renal Dialysis, Coronary Angiography, Catheterization, Bundle-Branch Block, Recombinant Proteins, Coronary Vessels, Tissue Plasminogen Activator, Renal Insufficiency, Chronic


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